To explore the hypothesis that exposure to neoadjuvant chemotherapy might alter gene expression in the ipsilateral non-cancer samples, we tested the number and character of differentially expressed genes (DEGs) in all ipsilateral samples available from individuals with Erb-B2 Receptor Tyrosine Kinase 2/HER2 positive (HER2+) breast cancer, half of whom had received neoadjuvant chemotherapy. This evidence concerns the gene ERBB2 and cancer.